YTTRIUM (ALKYL)CYCLOPENTADIENYLS

Yttrium (III) tris(cyclopentadienyl) YCp3

  Tris(cyclopentadienyl)yttrium, YCp3 (and for comparison Y(MeCp)3, both with  H2O as O source) was applied as precursor for the ALD growth of cubic Y2O3 thin films on Si substrates at temperature as low as 175°C. YCp3 precursor was evaporated at 150°C/2-3mbar (higher compared to 110°C/2-3mbar evaporation temperature for Y(MeCp)3). The YCp3/H2O system resulted in the slight increase of the deposition rate of Y2O3 vs. deposition temperature (from 1.5 to 1.8 Å/cycle at 250 to 400 °C temperatures), whereasY(MeCp)3/H2O process gave a constant growth rate (1.2−1.3 Å/cycle) at 200−400°C. The ALD-type growth mode was maintained till 250°C (YCp3/H2O process), compared to 300 °C for Y(MeCp)3/H2O system. The crystallinity, morphology, and chemical composition of the obtained Y2O3 layers was studied by XRD, AFM, and TOF-ERDA, respectively. YCp3 resulted in 0.5 at.% C impurity levels at 300°C, compared to 0.2% for Y(MeCp)3. Only 1.8 at.% hydrogen was obtained in the YCp3/H2O-grown film, whereas Y(MeCp)3 gave 3.1 at. % H. The smoothest yttria layers were obtained at ≤250 °C with both precursors.[i]

[i] J. Niinistö, M. Putkonen, L. Niinistö, Chem. Mater., 2004, 16 (15), pp 2953–2958, DOI: 10.1021/cm040145v ,  "Processing of Y2O3 Thin Films by Atomic Layer Deposition from Cyclopentadienyl-Type Compounds and Water as Precursors” 

Yttrium (III) tris(methylcyclopentadienyl) Y(MeCp)3

Yttrium (III) tris(methylcyclopentadienyl) Y(MeCp)3 is considered to have the highest vapor pressure of any of the surveyed yttrium compounds. High vapor pressure of the MO is critical for achieving reasonable growth rates using it as a MOCVD precursor. Y(MeCp)3 was studied by 1H NMR spectroscopy (Fig.7): near 5.9 ppm hydrogen peaks from the cyclopentadienyl ring (labeled H’) and near 2.0 ppm hydrogen peaks from the methyl groups (labeled H) are observed. No any organic impurities were observed by NMR; however, some oxygen species in <100 ppm concentration were found.

Y(MeCp)3 (+H2O) for Y2O3 by ALD

    Yttrium (III) tris(methylcyclopentadienyl) Y(MeCp)3 (combined with H2O as oxygen source), and  for comparison Y(thd)3 (with O3 as oxidant) was applied for growth of Y2O3 layers by ALD ;  the growth rates were 1.2–1.3 and 0.23Å/cycle, respectively, illustrating the general tendency that RE-cyclopentadienyl complexes (with H2O as O source) result in significantly higher ALD growth rates compared to the conventional β-diketonate/O3 system. Moreover, the organometallic (including cyclopentadienyls) and nitrogen-coordinated precursors produced lower C and H impurity levels and better electrical characteristics in the resulting RE2O3 films. However, the use of the novel C- or N-coordinated precursors as ALD precursors is restricted by their poor thermal stability.[[i][PS1] ]

[i] J. Päiväsaari, J. Niinistö, P. Myllymäki, Ch. Dezelah, Ch.H. Winter, M. Putkonen, M. Nieminen, L. Niinistö, Rare Earth Oxide Thin Films, Topics in Applied Physics, 2007, Vol. 106, 15-32, DOI: 10.1007/11499893_2, “Atomic Layer Deposition of Rare Earth Oxides”

Y(MeCp)3 (+H2O) for YScO3 by ALD

   Tris(methylcyclopentadienyl)yttrium Y(MeCp)3, combined with tris(cyclopentadienyl)scandium ScCp3 (Cp = C5H5) and H2O as oxygen source, has been applied for the growth of  amorphous YScO3 thin films by atomic layer deposition (and for comparison alternative process using β-diketonate-type metal complexes M(thd)3 (M = Y, Sc; thd = 2,2,6,6-tetramethyl-3,5-heptanedionato) and ozone O3 as oxidant was performed. Deposition temperatures were 300 °C for the cyclopentadienyl precursor-based process (and 335–350 °C for the M(thd)3 precursor-based process). Metal precursor pulsing ratio and the number of deposition cycles were controlling film metal ratio and film thickness. The as-deposited YScO3 films were stoichiometric, smooth, amorphous, had high permittivity (14–16) and  contained <1 at.% H and <0.2 at.% carbon regardless of the precursor system used. The beginning of crustallization was 800 °C for the layers deposited using Y(MeCp)3/ ScCp3 precursor-based process,  whereas films deposited using M (thd)3 precursors still remained amorphous at 800 °C, but crystallized at 1000 °C (however, dielectric properties of the layers were significantly deteriorated by crystallization).[i]

[i]P. Myllymäki, M. Nieminen, J. Niinistö, M. Putkonen, K. Kukli, L. Niinistö, J. Mater. Chem., 2006,16, 563-569; DOI: 10.1039/B514083H, “High-permittivity YScO3 thin films by atomic layer deposition using two precursor approaches”, http://lib.tkk.fi/Diss/2010/isbn9789526034898/article1.pdf 

Yttrium tris(ethylcyclopentadienyl) Y(EtCp)3

      Tris(ethylcyclopentadienyl)yttrium, Y(EtCp)3 (combined wioth H2O vapor as oxygen source) was used for the deposition of  yttria Y2O3 thin films on Si by ALD; the precursor evaporation conditions were 120°C/ 0.6-2 mbar. Film growth kinetics was investigated; growth rate was constant with number of deposition cycles, at optimal ALD conditions being 1.7±0.1 Å/cycle. However, gradual increase in growth rate was observed whene increasing the reactor temperature from 200 to 400°C, with a narrow plateau at ca.~250–285°C. Y2O3 films were stoichiometric with no detectable C contamination as per XPS data); as-deposited Y2O3 layers were polycrystalline (according to glancing incidence XRD).[[i]]

[i] Prodyut Majumder, Gregory Jursich, Adam Kueltzo, Christos Takoudis,  J. Electrochem. Soc., Volume 155, Issue 8, pp. G152-G158 (2008) Atomic Layer Deposition of Y2O3 Films on Silicon Using Tris(ethylcyclopentadienyl) Yttrium Precursor and Water Vapor”

Yttrium tris(isopropylcyclopentadienyl) Y(iPrCp)3

    Tris(isopropylcyclopentadienyl)yttrium Y(iPrCp)3 has been applied as precursor for the growth of yttrium sesquioxide (Y2O3) thin films (ca. 2µm thickness)  on a glass substrate by MOCVD, using Ar as carrier gas and CO2/H2 mixture as oxidant, with mole fractions of Y(iPrCp)3 7.5 X10~4 and CO2 ~1x10-2,  respectively.

    The authors also suggested that thin layers of yttrium phosphide, yttrium arsenide and yttrium antimonide, could be potentially deposited using Y(iPrCp)3 as precursor, combined with these precursors for nonmetallic elements are as follows: phosphorous, triethylphosphine (for P), arsenic, AsMe3 (for As), antimony, and SbMe3 (for Sb). [[i]]

[i][i] Ahmet Erbil , « Chemical vapor deposition of group IIIB metals », Patent number: US4882206, Filing date: 22 Jun 1988, Issue date: 21 Nov 1989, http://www.google.de/patents?id=wK43AAAAEBAJ&pg=PA6&zoom=4&dq=ytterbium+isopropylcyclopentadienyl+CVD&output=text#c_top

Yttrium tris(n-butylcyclopentadienyl) Y(n-BuCp)3

    Tris(n-butylcyclopentadienyl) yttrium Y(n-BuCp)3 is liquid and has higher vapor pressure vs. Y(MeCp)3 ; it was applied for the MOCVD growth of Y-Ga-N (YGN) thin films on GaN at 1050°C. The (n-BuCp)3Y precursor was used without purification to check the transport to the reactor; for best delivery the Y (n-BuCp)3 bubbler had to be heated to 110 °C (gas lines  from the bubbler to the growth chamber were covered with heating tape; strong evidence for the delivery of Y(t-BuCp)3Y precursor was observed, whereas for Y(MeCp)3 precursor there was no evidence delivery to the growth chamber was observed [[i]]

[i] DD Koleske, JR Creighton, SR Lee, MH Crawford… - 2009 - prod.sandia.gov, "Issues associated with the metalorganic chemical vapor deposition of ScGaN and YGaN alloys"

http://prod.sandia.gov/techlib/access-control.cgi/2009/094419.pdf

Yttrium (I) pentamethylcyclopentadienyl cyclooctatetraene adduct Y(CpMe5)(COT)

   Yttrium cyclooctatetraenyl-pentamethylcyclopentadienyl sandwich complexes Y(CpMe5)(COT) (or Y(Cp*)(COT) ) were applied as novel volatile precursor for the growth of Y2O3 thin films by PECVD (forming pure Y2O3 films in Ar/O2 and Ar/H2O plasmas, in N2O, and CO2 at substrate temperatures of 350–400° C and power densities of 1.0–1.5 W/cm2. The evaporation conditions of the precursor were 160°C/0.3mbar. The prepared layers were characterized by XPS, FTIR, SEM micrographs, CTEM electron diffraction, as well as metal analysis, carbon analysis.[i]

[i] A. Weber, H. Suhr, H. Schumann and R.-D. Köhn, Appl.Phys.A:Mat.Sci.& Processing, Vol.51, No.6 (1990),520-525, DOI: 10.1007/BF00324736 , “Thin yttrium and rare earth oxide films produced by plasma enhanced CVD of novel organometallic π-complexes” 

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